GogoShellKiller.java

   1 package org.argeo.cms.internal.kernel;
   2
   3 /**
   4  * Workaround for killing Gogo shell by system shutdown.
   5  *
   6  * @see https://issues.apache.org/jira/browse/FELIX-4208
   7  */
   8 class GogoShellKiller extends Thread {
   9
  10         public GogoShellKiller() {
  11                 super("Gogo Shell Killer");
  12                 setDaemon(true);
  13         }
  14
  15         @Override
  16         public void run() {
  17                 ThreadGroup rootTg = getRootThreadGroup(null);
  18                 Thread gogoShellThread = findGogoShellThread(rootTg);
  19                 if (gogoShellThread == null)
  20                         return;
  21                 while (getNonDaemonCount(rootTg) > 2) {
  22                         try {
  23                                 Thread.sleep(100);
  24                         } catch (InterruptedException e) {
  25                                 // silent
  26                         }
  27                 }
  28                 gogoShellThread = findGogoShellThread(rootTg);
  29                 if (gogoShellThread == null)
  30                         return;
  31                 // No non-deamon threads left, forcibly halting the VM
  32                 Runtime.getRuntime().halt(0);
  33         }
  34
  35         private ThreadGroup getRootThreadGroup(ThreadGroup tg) {
  36                 if (tg == null)
  37                         tg = Thread.currentThread().getThreadGroup();
  38                 if (tg.getParent() == null)
  39                         return tg;
  40                 else
  41                         return getRootThreadGroup(tg.getParent());
  42         }
  43
  44         private int getNonDaemonCount(ThreadGroup rootThreadGroup) {
  45                 Thread[] threads = new Thread[rootThreadGroup.activeCount()];
  46                 rootThreadGroup.enumerate(threads);
  47                 int nonDameonCount = 0;
  48                 for (Thread t : threads)
  49                         if (t != null && !t.isDaemon())
  50                                 nonDameonCount++;
  51                 return nonDameonCount;
  52         }
  53
  54         private Thread findGogoShellThread(ThreadGroup rootThreadGroup) {
  55                 Thread[] threads = new Thread[rootThreadGroup.activeCount()];
  56                 rootThreadGroup.enumerate(threads, true);
  57                 for (Thread thread : threads) {
  58                         if (thread.getName().equals("Gogo shell"))
  59                                 return thread;
  60                 }
  61                 return null;
  62         }
  63
  64 }